Electromagnetic device



une' 14 1927o J H. Q. HARRHSON ELECTROMAGNETIC DEVICE Filed Nov. 30, 1925 La@ F im;

Patented June 14, 1927.

UNITED STATES PT OFFICE.

HENRY C. HARRISON, OF PORT WASHINGTON, NEW YORK. ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEV YORK, N. Y., A CORPORATION OF N EW YORK.

ELECTROMAGNETIC DEVICE.

This invention relates to electromagnetic devices suitable for loud speaking receivers, phonographic recorders and the like.

The object of the invention is to provide an electromagnetic system capable of translating electrical vibrations into acoustical or mechanical vibrations or vice versa with minimum distortion.

In accordance with one of its features, the invention provides an electromagnetic system so arranged that eddy current losses are induced in thevibratory member and utilized to dampen its vibrations, to prevent distortion in the vibrations produced. In general, this feature consists in the provision of a centrally supported closed coil of one turn carrying a steady current, each end of the coil being adapted to vibrate in a steady magnetic field.`

The rdistortions are further reduced by roviding a mounting for the coil resilient in the direction of normal movement of the coil butl resistant tomovement in otherdirections, this mounting consisting of supports of comparatively7 thin sheet metal having a plurality of radial vanes formed integral therewith byv shearing sections and turning the Sheared portions at right angles to the plane of the support.

Referring to the drawing, Fig. 1 is a per,- spective view of an electromagnetic device embodying this invention applied to loud speaking receivers embodying the invention. Fig. 2 is an electromagnetic device embodying the invention adapted to recorders or reproducers.

Fig. l3 is a cross-sectional view of an electromagnetic device as shown in Fig. 1 showingthe circuit diagrammatically.

Fig. 4 is an enlarged detail view showing the support for the vibratory member.

Fig. 5 is a section through thesupport.

Cores 5 and 6 which may be supported in `a case (not shown) are E-shaped having arms 7, 8 and 9, and 10, 11 and 12, respectively. The middle arms 8 and 11 are provided With line coils 13 and 14, respectively. Supported between the cores 5 and 6 and insulated therefrom are members 15 and 16, provided with lugs 17 and 18, respectively, to which electrical connections may be made. The members 15 and 16 have spider-shaped portions 19 and 20, respectively intermediate their ends, the vanes being formed by shear- Sclial No. 6??,829.

ing the metal radiall \v and turning the sheared portion at. right angles to the plane of members 15 and 16, thereby p"oviding:ra

`dially extending vanes which are comparatively flexible in the plane of members 19 and 20 and rigid in planes atI right angles thereto. To the centers of the spider portions are attached studs 2l and 22 carrying a closed circuiti coil 28 of any light non-magnetic metal such as aluminum adapted to vibrate between the arms of the cores 5 and 6. One end ofthe coil 23 is provided with an extension 24 to which a diaphragm 2G may be connected by means of a link 25. In the modification shown in Fig. 2 a stylus holder 30 for, a recording stylus 81 is mounted directly on the coil 23.

In the preferred embodiment of the in.

vention the vibratory coil 23 is connected through its supports to a source of energy 32 which provides a steady current in opposite directions through each section of the coil 23. The coils 13and 14 are connected in series with the secondary of the transformer 35 and hence the alternating current induced in them by means of a translating device 34 with its energy source 33 produces forces which tend to make the coil 23 vibrate. A source of energy 3G is connected between the middle point of the. secondary and the common terminal between the coils 13 and 14 providing a steady current in coil 13 opposite to that in coil 14. The polarity of the core 5 due to the steady current is therefore opposite to that of the core 6, and hence when coil 23 vibrates E. M. Fs. in the same direction are set up in its two halves by this fiux which4 produce damping currents. The E. M. Fs. due to the vibration of coil 23 in the alternating fields arc in opposite directions and hence do not set up damping currents.

Obviously separate coils may be placed upon the cores 5 and 6 for the steady current instead of using the push-pull circuit shown.

That is claimed is:

l. An electromagnetic system for producing distortionless vibrations comprising an electromagnet providing a variable magnetic field, a coil movable in andv transverse said field and a source of steady current for said coil.

2. An electromagnetic system for producing distortionless vibrations comprising a magnet, a movable short-circuited coil in the field of said magnet, and a source of steady current for said coil.

3. An electromagnetic system for producing distortionless vibrations comprising an electromagnet, a movable short-circuited coil disposed in the field of said magnet, means for supporting said coil whereby it may oscillate about an axis in the plane ot said coil, a source of steady current for said coil, the current flowing in the opposite directions from the axis through said coil.

4. An electromagnetic system for producing' distortionless vibrations comprising a pair of electromagnets, a centrally supported movable coil, one .end of which is in the field of one magnet and the opposite end in the field of a second magnet, a source of steady current, and means whereby the current is supplied to the opposite ends ot' the coil in parallel.

5. In an electromagnetic device, a shortcircuited coil of non-magnetic material` a resilient support for said 'coil the aXi's of support lying in the plane of the coil, and elcctromagnets associated with ends of said coil.

6. In an electromagnetic device, a pair of spaced E-shaped electromagnets, a short-circuited coil of nonfmagnetic material resiliently supported at its center between said magnets 'and insulated therefrom, one end ot' said coil beingin the field of one magnet, andl the other end in the lield of the other magnet.

7. In an electromagnetic device a magnet providing a variable magnetic field, a shortcircuited coil disposed in .said field, and means for movably supporting said coil.

8. In an electromagnetic device, a Vibrio tortisliort-circuited coil, of one turn, a source of energy supplying a steady currentl in opposite directions through parts of said coil electromagnets in operative relation to cach part ot' said coil, and means providing a stead \v and a variable magnetic field in said magnets.

In Witness wher-cot. I hereunto subscribe my name this 21st day of November A.'D.,

HENRY C.l HARRISON.

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